1. Technical Field of the Invention
The invention concerns a transmitting device, a transmitting unit and an optical transmission system for optically transmitting analog electrical signals.
2. Discussion of Related Art
The analog signals are television signals for example. An optical transmission system for optically transmitting television signals is known from the article "Diamond-A digital optical television distribution network" in the publication `telecom praxis` 2/1993, pages 38 to 45. The television signals have a bandwidth of 7 MHz to 14 MHz. They are usually converted from analog to digital by means of pulse code modulation, then multiplexed electrically and converted electrical-to-optical; one optical pulse usually corresponds to one electrical pulse and thus to one bit. The now optical digital television signals are transmitted to several receiving devices via a passive optical transmission network of glass-fibers, i.e., optical fibers, and optical splitters. Each receiving device includes optical-to-digital converters and a digital-to-analog converter for recovering the analog electrical signals. The number of multiplexed television signals is limited by the resolution and speed of the available digital-to-analog converters. Each digital-to-analog converter is an active unit which must be controlled and synchronized.